experts say every part matters to maintaining the integrity of a structure. >> translator: even such a small part, i mean, bolts, caused this serious accident. i think the operators should review what they're doing to maintain safety. >> reporter: officials say 12 tunnels across the country have the same structure as the one that collapsed. the government has ordered inspections. japan has more than 350 tunnels that are 30 years or older. experts say operators must check all of the structures to make sure they are safe.